58 
PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA 
fe 
of asset in different industries [10]. We have not yet reached 
the stage of replacing this physical determination of scrapping 
by an economic one. 
b) Endogenous final demand. 
This category can be divided into three components. 
1) Industrial extensions. These are based on a calculation 
of the type of (IV. 25) and thus involve projected input-output 
matrices, both current and capital, as well as levels and growth 
rates of exogenous final demand. The capital coefficients were 
estimated with the help of the material relating to the years 
[948-1960 brought together in [10], amended in many cases 
in the light of outside information. 
2) Investments in stocks. These are related to changes 
in output levels on the basis of experience in the 1950’s. 
3) Imports. These are based on a calculation of the type 
of (IV. 26). The first step is to set a figure on the balance of 
trade to be aimed at in the future. If this is subtracted from 
export proceeds, the total value of imports is obtained. 
Complementary intermediate imports are estimated by fixed 
coefficients applied to the outputs of the various using in- 
dustries, in exactly the same way as any other form of inter- 
mediate input. These coefficients are based on postwar trends 
and at present are very rough, because the classification of 
imports has only been carried out for the three years 1948, 
1054 and 1960. 
Individual groups of competitive imports, as explained in 
section 3(c) above, are treated as linear functions of the total 
amount of money available for competitive imports as a whole. 
These coefficients are roughly assessed on the basis of recent 
experience. 
Considerable improvements could be made in all these 
estimates simply by a more thorough analysis of existing 
1] Stone - pag. 66